Aberrant constitutive activation of nuclear factor κB in glioblastoma multiforme drives invasive phenotype

Several recent studies have shown that aberrant constitutive activation of nuclear factor kappaB (NF-κB) is present in a variety of cancers including gliomas. NF-κB is known to play important roles in the physiological regulation of diverse cellular processes such as inflammation, growth and immunity. In contrast, aberrant activation of this latent transcription factor promotes cancer cell migration, invasion and resistance to chemotherapy. Here we show by electro-mobility shift assay (EMSA) and immuno-staining that constitutive NF-κB activation is present in various malignant glioma cell lines as well as in primary cultures derived from tumor tissue. This activation was not serum dependent and it led to high IL-8 gene transcription and protein production. Over-expression of an I-κB super-repressor (I-κB SR) transgene completely blocked constitutive NF-κB activation, nuclear localization and transcription of some but not all NF-κB regulated genes indicating that NF-κB signaling in glioma cells is I-κB dependent. Surprisingly, over-expression of IκBSR did not have any effect on the transcription levels of anti-apoptotic genes in these glioma cultures and cell lines. Down-regulation of NF-κB activation reduced invasion of glioma cells through matrigel. Collectively these data suggest that aberrant constitutive activation of NF-κB in glioblastoma cells promotes their invasive phenotype. Interruption of this aberrant NF-κB activity may help reduce the spread of this infiltrative tumor.